The invention mainly applies to the connection of electric cables having a light metal, such as aluminium, core, covered by an insulating sheath. However, it can also be used for the connection of cables, whose core is made from any other material such as copper, particularly when it is desirable to have a sealing of the connection and/or when it is wished for the connection to take place in a non-aggressive manner for the cable.
In industries such as the aeronautical industry requiring considerable electric cable lengths and for which financial and/or weight gains are desired, certain large cross-section, copper core cables have for some time been replaced by aluminium core cables. Thus, despite the need to use aluminium core cables with a larger cross-section for compensating a reduced conductivity compared with that of copper, the mass balance gives a gain of approximately 50%.
In order to take greater advantage of the weight gain resulting from the use of aluminium core cables, it would be logical to also replace smaller cross-section copper core cables by aluminium core cables. This more particularly relates to the copper core cables between gauge 10 (4.9 mm.sup.2 cross-section) and gauge 24 (0.2 mm.sup.2 cross-section).
However, although the tensile strength difference between the two materials causes no particular problems with cables with a cross-section greater than 5 mm.sup.2, it becomes critical for cables having a smaller cross-section. Thus, the forces exerted on the cables, particularly when producing cable bundles, may then be prejudicial to the electrical continuity of the circuits and therefore to the safety of aircraft.
Another problem relates to the sensitivity of aluminium to chemical attacks. This sensitivity makes it necessary for the connection between the aluminium cable and the copper contact to be tight, so as to insulate the aluminium from the ambient medium, which is not necessary when a copper cable is used.
However, bearing in mind the larger diameter of aluminium core cables compared with copper core cables for an equivalent resistivity, any diameter increase of the contacts for ensuring the sealing and tensile strength of the connection makes it difficult or even impossible to use the standardized tools necessary for the fitting and unlocking of contacts, when use is made of the most widely used connectors where the contacts are unlocked from the rear.
Moreover, an increase in the diameter of the cavities formed on standardized connectors for receiving the standardized contacts is difficult to envisage without a modification to the location of the cavities, as a result of the proximity thereof to the existing connectors. However, a modification to the positions of the cavities would be the equivalent of rendering obsolete all the presently used, standardized connectors.
Finally, a change in the connection technology for the use of contacts with unlocking from the front would require important modifications and the creation of novel connectors, which is clearly not desirable.
GB-A-977,466 proposes the connection of an electric cable to an end member such as an electric contact by introducing the end of the cable into a blind hole or bore having a uniform diameter and machined in a connection zone of the end member. The outer surface of said connection zone is initially a truncated cone-shaped surface, whose diameter increases towards the open end of the hole. The end member is made from a ductile metal, so that a radial compacting force exerted on the connection zone has the effect of giving the outer surface of said zone a uniform diameter, cylindrical shape. Thus, a mechanical connection is formed, which opposes the separation of the end member and the cable.
However, the solution described in GB-A-977,466 is not applicable to an aluminium core cable with a cross-section below 5 mm.sup.2 in view of the limited tensile strength of such a cable. In addition, no matter what the nature of the metal from which the cable is made, the solution described in GB-A-977,466 does not make it possible to obtain a tight connection.
The main object of the invention is a process making it possible to connect an electric cable, such as a small cross-section aluminium core cable, to an end member such as an electric contact so as to ensure a stable and reliable electrical connection, a satisfactory mechanical strength and the necessary sealing with respect to the external ambient, without complicating implementation, without rendering obsolete the presently used, standardized connection systems and whilst retaining to the greatest possible extent the use of existing tools.